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CVE-2021-31755

96
FAUCET Score

CVE-2021-31755 is a critical stack buffer overflow vulnerability affecting Tenda AC11 routers with firmware through version 02.03.01.104_CN. This flaw allows unauthenticated attackers to execute arbitrary code on the system by sending a specially crafted POST request to the /goform/setmac endpoint. With a CVSS score of 9.8 (CRITICAL) and an EPSS score indicating high exploitability, the vulnerability poses a severe risk, enabling full compromise of affected devices. It is actively exploited in the wild, listed in CISA's KEV catalog, and has garnered significant community attention, including the availability of Nuclei templates for detection.

Impacted Technologies

VendorProductVersion(s)CPE
<= 02.03.01.104_cnCPE matchmatch criteria
cpe:2.3:o:tenda:ac11_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
85.85%
Probability of exploitation in next 30 days
EPSS Percentile
99.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Added to KEV · Nov 3, 2021
Nuclei: CVE-2021-31755 · Jul 15, 2021
This CVE's current EPSS score of 0.8585 is in the 99th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
github.com / Yu3H0/IoT_CVE/tree/main/Tenda/CVE_3
Broken LinkExploitIssue TrackingThird Party Advisory